Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Subject: search.filters.subject.Affine gravity

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  • Article
    Citation - WoS: 22
    Citation - Scopus: 24
    Are There Really Conformal Frames? Uniqueness of Affine Inflation
    (World Scientific Publishing Co. Pte Ltd, 2018) Azri, Hemza
    Here, we concisely review the nonminimal coupling dynamics of a single scalar field in the context of purely affine gravity and extend the study to multifield dynamics. The coupling is performed via an affine connection and its associated curvature without referring to any metric tensor. The latter arises a posteriori and it may gain an emergent character like the scale of gravity. What is remarkable in affine gravity is the transition from nonminimal to minimal couplings which is realized by only field redefinition of the scalar fields. Consequently, the inflationary models gain a unique description in this context where the observed parameters, like the scalar tilt and the tensor-to-scalar ratio, are invariant under field reparametrization. Overall, gravity in its affine approach is expected to reveal interesting and rich phenomenology in cosmology and astroparticle physics.
  • Article
    Citation - WoS: 47
    Citation - Scopus: 42
    Affine Inflation
    (American Physical Society, 2017) Azri, Hemza; Demir, Durmuş Ali
    Affine gravity, a gravity theory based on affine connection with no notion of metric, supports scalar field dynamics only if scalar fields have nonvanishing potential. The nonvanishing vacuum energy ensures that the cosmological constant is nonvanishing. It also ensures that the energy-momentum tensor of vacuum gives the dynamically generated metric tensor. We construct this affine setup and study primordial inflation in it. We study inflationary dynamics in affine gravity and general relativity, comparatively. We show that nonminimally coupled inflaton dynamics can be transformed into minimally coupled ones with a modified potential. We also show that there is one unique frame in affine gravity, as opposed to the Einstein and Jordan frames in general relativity. Future observations with higher accuracy may be able to test affine gravity.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 3
    Affine Dynamics With Torsion
    (Springer Verlag, 2016) Gültekin, Kemal
    In this study, we give a thorough analysis of a general affine gravity with torsion. After a brief exposition of the affine gravities considered by Eddington and Schrödinger, we construct and analyze different affine gravities based on the determinants of the Ricci tensor, the torsion tensor, the Riemann tensor, and their combinations. In each case we reduce equations of motion to their simplest forms and give a detailed analysis of their solutions. Our analyses lead to the construction of the affine connection in terms of the curvature and torsion tensors. Our solutions of the dynamical equations show that the curvature tensors at different points are correlated via non-local, exponential rescaling factors determined by the torsion tensor.